WO2022045340A1

WO2022045340A1 - Electric motor

Info

Publication number: WO2022045340A1
Application number: PCT/JP2021/031814
Authority: WO
Inventors: チャイリーカンパナート; パンウォラポットアーティット; 慎悟鈴木; 智則小嶋; 洋一田邉
Original assignee: 株式会社富士通ゼネラル
Priority date: 2020-08-31
Filing date: 2021-08-31
Publication date: 2022-03-03
Also published as: JP2022041317A; JP6984704B1

Abstract

[Problem] To provide an electric motor that easily adjusts the electrostatic capacitance between the stator and rotor sides of the electric motor and suppresses the occurrence of electrolytic corrosion. [Solution] One embodiment of this electric motor comprises: a rotor; a shaft positioned along the axis of rotation of the rotor, the rotor being secured to the shaft; a first bearing positioned on one end side of the shaft; a second bearing positioned on the other end side of the shaft; a stator core positioned on the outer circumferential side of the rotor; a resin outer shell that covers the stator core; and an electrical continuity member for electrically connecting the respective outer rings of the first and second bearings with each other. An electroconductive member that covers at least a portion of the electrical continuity member is attached to the surface of the resin outer shell.

Description

Electric motor

The present invention relates to an electric motor including two bearing houses and a conductive member that conducts the bearing houses to each other.

Conventionally, as an electric motor, an inner rotor type motor in which a cylindrical rotor having a permanent magnet is arranged coaxially with the stator on the inner diameter side of a cylindrical stator that generates a rotating magnetic field is known. This electric motor is used, for example, for rotationally driving a blower fan mounted on an air conditioner.

When this motor is driven by a PWM type inverter that performs high frequency switching, a potential difference (shaft voltage) is generated between the inner ring and the outer ring of the bearing. When this shaft voltage reaches the breakdown voltage of the oil film inside the bearing, a current flows inside the bearing and causes electrolytic corrosion in the bearing.
As a conventional technique for suppressing the generation of electrolytic corrosion, the axial voltage is reduced and the generation of electrolytic corrosion is suppressed by adjusting the capacitance on the stator side of the motor to be approximately equal to the capacitance on the rotor side. Is known (Patent Document 1).
In Patent Document 1, the capacitance is adjusted by dividing the rotor core into an inner core and an outer core and providing a dielectric (insulator) layer between them.

Japanese Unexamined Patent Publication No. 2014-124082

Here, in a structure in which the rotor core is divided and a dielectric is sandwiched between them, the thickness and shape of the insulating layer are determined by the mold forming the rotor core, and when adjusting the capacitance, the mold is changed and the rotor core is used. Cutting etc. is required. Therefore, there is a problem that the capacitance cannot be easily adjusted after the mold of the rotor core is completed.

Therefore, an object of the present invention is to provide an electric motor capable of easily adjusting the capacitance between the stator side and the rotor side of the electric motor to suppress the occurrence of electrolytic corrosion.

One aspect of the motor of the present invention includes a rotor, a shaft arranged along the rotation axis of the rotor and fixed to the rotor, a first bearing arranged on one end side of the shaft, and the above. A second bearing arranged on the other end side of the shaft, a stator core arranged on the outer peripheral side of the rotor, a resin outer shell covering the stator core, and outer rings provided by each of the first bearing and the second bearing. It is provided with a conductive member for electrically connecting the bearings. A conductive member that covers at least a part of the conductive member is attached to the surface of the resin outer shell.

According to the present invention, the capacitance between the stator side and the rotor side of the motor can be easily adjusted to suppress the occurrence of electrolytic corrosion.

It is a perspective view of the rotor of the electric motor which concerns on this invention. It is a perspective view of the stator of the motor which concerns on this invention. It is a top and bottom perspective view which shows the electric motor without a conductive sheet which concerns on this invention. It is a front view and the component development view of the 2nd bearing of the electric motor which concerns on this invention. It is a side perspective view which shows the electric motor which concerns on this invention. It is a cross-sectional view which shows the coupling of the electric motor and the capacitance which concerns on this invention. It is a bottom view which shows the electric motor which concerns on this invention. It is a non-grounded bridge type equivalent circuit diagram of the electric motor which concerns on the present invention with respect to a capacitance. It is an output waveform of the shaft voltage in the motor which concerns on this invention without a conductive sheet. It is an output waveform of the shaft voltage when the conductive sheet is attached to the motor which concerns on this invention. It is a graph which showed the stator capacitance with respect to the area change of the conductive sheet which concerns on this invention. It is a partial side perspective view which shows the electric motor without a conductive sheet which concerns on this invention. It is a graph which showed the stator capacitance with respect to the change of the width of the conduction member which concerns on this invention. It is a partial side perspective view which shows the electric motor with a conductive sheet which concerns on this invention. It is a graph which showed the stator capacitance with respect to the area change of the conductive member and the conductive sheet which concerns on this invention.

Next, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings below, the same or similar parts are designated by the same or similar reference numerals. However, it should be noted that the drawings are schematic and may differ from the actual ones. Therefore, specific components should be judged in consideration of the following explanations.

Further, the embodiments shown below exemplify devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention describes the shape, structure, arrangement, etc. of components. It is not specific to the following. The technical idea of the present invention may be modified in various ways within the technical scope specified by the claims described in the claims.

The electric motor according to the embodiment of the present invention will be described below.

<Overall configuration of motor>
1 to 6 are diagrams illustrating the configuration of the electric motor 1 in the present embodiment. As shown in these figures, the electric motor 1 is, for example, a brushless DC motor. Although not shown, the electric motor 1 is used, for example, to rotationally drive a blower fan mounted on an outdoor unit of an air conditioner.

As shown in FIG. 6, the motor 1 in the present embodiment includes a stator (stator) 2, a rotor (rotor) 3, a motor outer shell (resin outer shell) 10, a bracket 41, and a conduction member 5. I have.
In the following, an inner rotor type permanent magnet motor 1 in which a cylindrical rotor 3 having a permanent magnet portion 31 is rotatably arranged inside a cylindrical stator 2 that generates a rotating magnetic field is taken as an example. explain.

<Stator, rotor and motor outer shell>
As shown in FIG. 6, the rotor 3 is rotatably arranged with a predetermined gap on the inner peripheral side of the stator core 21 of the stator 2. The rotor 3 is a surface magnet type in which a permanent magnet 31 is arranged in an annular shape on an outer peripheral surface facing the stator core 21.
As shown in FIGS. 1 and 6, the permanent magnet 31 is fixed around the shaft 32 via the outer peripheral side iron core 32, the insulating member 33, and the inner peripheral side iron core 35. The shaft 32 is supported by a first bearing 33 and a second bearing 34. Then, each of the bearing accommodating portion 42 (bracket 41) described later in which the first bearing 33 is accommodated and the second bearing accommodating portion 43 described later in which the second bearing 34 is accommodated are housed in the resin motor outer shell 10. By being fixed, the rotor 3 is rotatably supported.

The permanent magnet 31 is formed in an annular shape by a plurality of (for example, 8 or 10) permanent magnet pieces 311 so that the N pole and the S pole appear alternately at equal intervals in the circumferential direction. As the permanent magnet 31, a plastic magnet formed in an annular shape by solidifying the magnet powder with a resin may be used.

The outer peripheral side iron core 32 is formed in an annular shape and is located on the inner diameter side of the permanent magnet 31. On the outer peripheral side iron core 32, in order to position the permanent magnet 31, a plurality of (for example, 10 pieces in the circumferential direction) outer peripheral side protrusions (for example, 10 pieces in the circumferential direction) protruding from the outer peripheral surface of the outer peripheral side iron core 32 toward the outer diameter side (not shown). It is equipped with. For example, the outer peripheral side protrusion is formed so as to extend from one end to the other end of the outer peripheral side iron core 32 in the central axis direction.

The inner peripheral side iron core 35 is formed in an annular shape and is located on the inner diameter side of the outer peripheral side iron core 32. Further, the center of the inner peripheral side iron core 35 is provided with a through hole penetrating in the direction of the central axis. The shaft 32 is fixed to a through hole provided in the inner peripheral side iron core 35 by press fitting or caulking.
The inner peripheral side iron core 35 may be provided with a plurality of through holes (not shown) for lightening the weight between the through hole and the outer peripheral surface of the inner peripheral side iron core 35. .. These plurality of through holes are arranged at equal intervals in the circumferential direction so that the shape of the inner peripheral side iron core 35 in which the through holes are formed becomes a spoke shape when viewed from the central axis direction.

The insulating member 33 is made of a dielectric resin such as PBT (polybutylene terephthalate) or PET (polyethylene terephthalate), and is located between the outer peripheral side iron core 32 and the inner peripheral side iron core 35. The insulating member 33 is integrally molded with the outer peripheral side iron core 32 and the inner peripheral side iron core 35 by insert molding in which a resin is filled between the outer peripheral side iron core 32 and the inner peripheral side iron core 35.
By providing the insulating member 33, the capacitance between the outer peripheral side iron core 32 and the inner peripheral side iron core 35 (a part of the capacitance between the winding of the stator 2 and the shaft 32) can be made smaller. At this time, the capacitance between the outer peripheral side iron core 32 and the inner peripheral side iron core 35 depends on the thickness (diameter length) of the insulating member 33. The electric motor 1 in which the capacitance on the rotor 3 side is adjusted by the thickness of the insulating member 33 is the

inner ring

334 and 344 side by matching the capacitance on the stator 2 side and the capacitance on the rotor 3 side. The potential difference between the outer ring 332 and the outer ring 332 and 342 is adjusted to be small, thereby preventing electrolytic corrosion of the bearing.
In this embodiment, the rotor core of the rotor 3 has a structure in which two cylindrical cores, an inner peripheral side core 32 and an outer peripheral side iron core 35, are connected by an insulating member 33, but the structure of the rotor core is Is not limited to this. For example, the rotor core may not be provided with the insulating member 33, and may be formed from one cylindrical core.

The stator 2 is wound around a stator core (stator core) 21 having a cylindrical yoke portion (not shown) and a plurality of teeth portions (not shown) extending from the yoke portion to the inner diameter side, and a teeth portion via an insulator. It has a winding (not shown). The stator 2 is covered with a motor outer shell 10 (resin outer shell) made of resin except for the inner peripheral surface of the stator core 21 by resin integral molding (see FIG. 2).
That is, the motor outer shell 10 covers the stator 2 provided with the stator core 21 and the winding, and accommodates the rotor 3 inside. The stator 2 is arranged on the outer peripheral side of the rotor 3 (outside in the radial direction of the permanent magnet motor 1). Further, the stator core 21 of the stator 2 is arranged so that the teeth portion of the stator core 21 faces the permanent magnet portion 31 of the rotor 3 in the radial direction. In other words, the stator 2 is arranged so that the annular permanent magnet portion 31 included in the rotor 3 faces the stator core 21 of the stator 2 in the radial direction.

The motor outer shell 10 as the main body may have any shape, but for example, the central axis of the permanent magnet motor 1, that is, one end side (hereinafter, the rotation axis C) of the rotation axis of the rotor 3 in the axial direction (shaft 32). It is formed in a bottomed cylindrical shape having an opening O on the output side). In this embodiment, the motor outer shell 10 includes an opening O and an end surface portion (bottom surface) 13 formed at an end portion on the opposite side of the opening O (the counter-output side of the shaft 32).
The motor outer shell 10 is formed of, for example, a BMC (Bulk Molding Compound: unsaturated polyester resin) resin. The motor outer shell 10 does not need to be entirely formed of an insulating material such as resin, and a part of the motor outer shell 10 may be formed of a metal such as a conductive material. Further, in this embodiment, the case where the appearance of the motor outer shell 10 is columnar is illustrated, but the appearance of the motor outer shell 10 may be a square pillar or a hexagonal pillar.

The rotor 3 is rotatably arranged on the inner peripheral side of the stator core 21 of the stator 2 with a predetermined gap between the stator core 21 and the stator core 21. As shown in FIGS. 1 and 6, the permanent magnet portions 31 arranged in an annular shape are arranged on the outer side (outer peripheral side) in the radial direction of the rotor 3 so as to face the stator core 21.

The rotor 3 is fixed around the shaft 32. The shaft 32 is rotatably supported (held) by a first bearing 33 and a second bearing 34 (bearings, bearings) fixed to the outer peripheral surface of the shaft 32.
Further, the rotor 3 rotates by accommodating (holding) the first bearing 33 in the first bearing accommodating portion 42 described later and accommodating (holding) the second bearing 34 in the second bearing accommodating portion 43 described later. It is supported freely. The first bearing accommodating portion 42 and the second bearing accommodating portion 43 are formed of, for example, a magnetic material of chromium nickel-based stainless steel.

<Bearing, bracket and bearing house>
As shown in FIG. 6, in the first bearing 33, the inner ring 334 side of the first bearing 33 is fixed to one end side (counter-output side) of the shaft 32. In the second bearing 34, the inner ring 344 side of the second bearing 34 is fixed to the other end side (output side) of the shaft 32. The first bearing 33 and the second bearing 34 (a pair of bearings) cooperate to rotatably support the shaft 32 and the rotor 3 connected to the shaft 32.

As the first bearing 33 and the second bearing 34, for example, a ball bearing composed of an outer ring 332, 342, an

inner ring

334, 344, a cage 346, a

ball

338, 348, and a shield 360 is used (FIGS. 1, 4, and 6). reference).

The bracket 41 includes a second bearing accommodating portion 43 accommodating the second bearing 34, and an end face portion 44 covering the opening O. The bracket 41 is arranged at one end in the direction of the rotation axis C, that is, on the output side of the shaft 32 in the motor outer shell 10 of the permanent magnet motor 1. The end face 44 of the bracket 41 and the second bearing accommodating portion 43 are integrally molded (see FIG. 6). The bracket 41 is formed, for example, by pressing a metal plate.
The bracket 41 is attached to the end of the motor outer shell 10 on the output side by crimping, screwing, or the like as a lid that covers the opening O of the motor outer shell 10. The opening O of the motor outer shell 10 may be opened toward the counter-output side. In this case, the bracket 41 is arranged not on the output side of the shaft 32 but on the opposite output side of the shaft 32.

The end face portion 44 of the bracket 41 is formed in a substantially disk shape in which the outer shape in the radial direction extends in the radial direction to the outer peripheral surface of the motor outer shell 10. Further, the end face portion 44 forms the outer shell of the permanent magnet motor 1 together with the outer shell 10 of the motor.

Further, in the central portion of the disk-shaped bracket 41, a second bearing accommodating portion (bearing house portion) 43 for accommodating the second bearing 34 is arranged on the inner side of the permanent magnet motor 1. (See FIGS. 3 (A) and 6). The second bearing 34 is arranged on the counter-output side of the permanent magnet motor 1 when viewed from the second bearing accommodating portion 43. The second bearing accommodating portion 43 is formed in a substantially bottomed cylindrical shape by, for example, pressing.

A first bearing accommodating portion (bearing house portion) 42 for accommodating the first bearing 33 is arranged on the inner side of the permanent magnet motor 1 in the central portion of the counter-output side end portion of the motor outer shell 10 (FIG. 3 (B) and 6). The first bearing 33 is arranged on the output side of the permanent magnet motor 1 when viewed from the first bearing accommodating portion 42. The first bearing accommodating portion 42 is formed in a substantially bottomed cylindrical shape, similarly to the second bearing accommodating portion 43.
The first bearing accommodating portion 42 is arranged inside (inner diameter side) of the annular permanent magnet portion 31 in the radial direction of the rotor 3. A connection portion 45 connected to the first bearing accommodating portion 42 is provided on the inner diameter side of the end face portion 13 of the resin motor outer shell 10 which is a non-magnetic material (see FIG. 6).

As shown in FIG. 6, the first bearing accommodating portion 42 has a tubular portion 421 that holds the outer ring 332 side of the first bearing 33 from the radial direction and a rotor from one end of the tubular portion 421 in the rotation axis C direction. An annular flange portion 422 extending radially outward (outer peripheral side) in No. 3 and a crown portion 423 extending radially inward (inner peripheral side) from the other end of the tubular portion 421 in the rotation axis C direction. , Have.
The crown portion 423 covers the other end side of the first bearing 33 in the rotation axis C direction. The outer peripheral edge of the annular flange portion 422 is located on the inner side (inner peripheral side) of the rotor 3 in the radial direction with respect to the permanent magnet portion 31. In other words, the first bearing accommodating portion 42 is formed so as not to overlap the permanent magnet portion 31 when viewed from the rotation axis C direction of the rotor 3.

The first bearing accommodating portion 42 is arranged inside (inner diameter side) in the radial direction of the rotor 3 with respect to the permanent magnet portion 31 when viewed from the rotation axis C direction. Further, the outer peripheral edge portion (edge portion on the outer diameter side) of the flange portion 422 of the first bearing accommodating portion 42 is covered with a resin which is a non-magnetic material.
That is, in the outer shell 10, the outer peripheral edge portion of the flange portion 422 of the first bearing accommodating portion 42 is covered with the resin connecting portion 45.

The first bearing accommodating portion 42 is arranged on the inner diameter side of the permanent magnet portion 31 in the radial direction of the rotor 3. Further, the outer peripheral edge portion of the flange portion 422 included in the first bearing accommodating portion 42 is covered with the end face portion 13 (connecting portion 45) of the motor outer shell 10 made of resin, which is a non-magnetic material. As a result, the leakage flux flowing from the permanent magnet 31 to the first bearing accommodating portion 42 can be suppressed.
The second bearing accommodating portion 43 is formed in the same shape as the first bearing accommodating portion 42, and has a tubular portion 431 that holds the outer ring 342 side of the second bearing 34 from the radial direction, and a rotating shaft C of the tubular portion 431. It has a crown 433 that extends radially inward from the other end in the direction.

The bracket 41 includes a cover main body 414 attached along the upper end surface of the stator 2 and a fitting portion 415 integrally formed with the cover main body 414. These cover body 414 and fitting portion 415 correspond to the above-mentioned end face portion 44.
The entire cover body 414 is formed in a disk shape as a whole. As shown in FIG. 6, the fitting portion 415 is formed as an annular protrusion arranged on the outer peripheral edge portion of the cover main body 414. As shown in FIGS. 3 (A) and 5, the fitting portion 415 is fitted to the output side end of the motor outer shell 10 (the upper end surface of the motor outer shell 10 in FIG. 6) from the rotation axis C direction. The motor outer shell 10 and the bracket 41 are axially aligned, and the second bearing 34 is housed in the second bearing accommodating portion 43 provided in the bracket 41.

A notch groove 108 for arranging the conductive member 5 is formed on the outer peripheral surface and the end surface of the motor outer shell 10 (see FIGS. 3 and 5). The notch groove 108 formed in the end surface 13 of the motor outer shell 10 extends from the vicinity of the center in the radial direction of the permanent magnet motor 1 to the outer edge portion. The notch groove 108 formed on the outer peripheral surface 14 of the motor outer shell 10 is formed so as to extend along the rotation axis direction of the permanent magnet motor 1 so as to be continuous from the notch groove 108 formed on the end surface 13.

<Conduction member>
When the motor 1 is driven by a PWM type inverter that performs high frequency switching, the neutral point potential of the winding does not become zero, and a voltage called a common mode voltage is generated. Due to this common mode voltage, the stray capacitance inside the motor 1 causes a potential difference (shaft voltage) between the

inner rings

334 and 344 of the first bearing 33 and the second bearing 34 and the outer rings 332 and 342, respectively. ..

When this shaft voltage reaches the breakdown voltage of the oil film inside the bearing, a current flows inside the bearing and causes electrolytic corrosion in the bearing. Electrolytic corrosion is a phenomenon in which a bearing is damaged by a discharge (electric spark) generated when the axial voltage between the

inner rings

334 and 344 of the first bearing 33 and the second bearing 34 and the outer rings 332 and 342 is high. When electrolytic corrosion occurs in a bearing, scratches on the rolling surface of the bearing cause abnormal noise when the bearing rotates, or the rotation efficiency of the motor is lowered.
In the motor 1 of the present embodiment, in order to suppress the occurrence of electrolytic corrosion in this bearing, a conduction member that conducts the first bearing accommodating portion 42 in which each of the two bearings is accommodated and the second bearing accommodating portion 43. It is equipped with 5.

The conductive member 5 is formed by processing, for example, a conductive material (for example, SUS304 of stainless steel) into a band shape or a wire shape. In this embodiment, the conductive member 5 is formed by bending a steel plate having a thickness of about 0.3 mm, which is punched out in a strip shape, into an L-shape or a U-shape along the outer surfaces of the motor outer shell 10 and the bracket 41 (. See FIGS. 3 and 6). The conductive member 5 has a spring characteristic in consideration of attachment to the motor 1.
The conduction member 5 has the first bearing 33 and the second bearing 33 by conducting the first bearing accommodating portion 42 in which the first bearing 33 is accommodated and the second bearing accommodating portion 43 in which the second bearing 34 is accommodated. The potentials of the outer rings 332 and 342 of the bearing 34 can be set to the same potential, and the occurrence of electrolytic corrosion can be suppressed by making the potential difference between the inner and outer rings of each bearing relatively small.

The conduction member 5 includes a connection end portion connected to the bearing

accommodating portions

42 and 43, an end face side arrangement portion arranged radially extending to the end surface 13 of the outer shell of the motor 1, and an outer peripheral surface 14 of the outer shell of the motor 1. Is provided with an outer peripheral surface side arrangement portion arranged along the rotation axis C direction. In this embodiment, the case where the conductive member 5 is formed of one strip-shaped member is illustrated, but a plurality of conductive members may be connected to form the conductive member 5.

As shown in FIGS. It is arranged so as to extend to the inside of the 415.
By arranging the conductive member 5 in the notch groove 108, the conductive member 5 does not project to the surface of the outer shell of the motor 1 and the conductive member 5 can be prevented from falling off from the motor 1.

The connection ends at both ends of the conduction member 5 are bent along the tubular connection portion 45 of the resin outer shell, the tubular portion 421 of the bearing house portion 42, and the fitting portion 415 of the bracket 41. For example, it is press-fitted and fixed.
As a result, both connecting ends of the conductive member 5 are fixed in contact with each of the flange portion 422 and the fitting portion 415 of the bearing house portion 42, so that the first bearing 33 and the second bearing 34 are brought into contact with each other. It is conducted.

The means for fixing both ends of the conductive member 5 to the bearing house portion is not limited to the above-mentioned means. For example, the connection end portion of the conductive member 5 may be fixed to the

bearing house portions

42, 43 by a caulking member (not shown).

As shown in FIG. 6, the capacitance (stator capacitance) Cs on the stator 2 side is between the stator 2 and the bracket 41, and the rotor 3 side is between the rotor 3 and the shaft 32. Capacitance (rotor capacitance) Cr, capacitance Cb1 between the inner ring 334 and the outer ring 332 of the first bearing 33, and capacitance between the inner ring 344 and the outer ring 342 of the second bearing 34. Cb2 is present. The capacitances Cb1 and Cb2 between the inner ring and the outer ring of each bearing are considered to be smaller than the stator capacitance Cs and the rotor capacitance Cr in consideration of size, mass, material and the like.

FIG. 8 is a non-grounded bridge type equivalent circuit diagram of the motor 1 with respect to these capacitances.
Here, the ground capacitance of the stator (stator) 2 is C1, the ground capacitance of the rotor (rotor) 3 is C2, the pulse voltage synchronized with the PWM frequency in the high frequency switching of the motor 1 is Vp, and the outer ring of the bearing. The shaft voltage between the inner ring and the inner ring is | Vs-Vr |.
At this time, the condition for minimizing the shaft voltage | Vs-Vr | is Cs · C2 = Cr · C1. Further, if the ground impedances of the stator 2 and the rotor 3 at the PWM frequency ω are Z1 = (1 / ωC1) and Z2 = (1 / ωC2), respectively, the ground impedance takes a very large value. C1 and C2 have relatively small values and can be approximated to C1≈C2. Therefore, the condition for minimizing the shaft voltage | Vs-Vr | is Cr = Cs. In the present embodiment, the permanent magnet motor 1 in a state where the capacitance on the rotor 3 side (rotor capacitance Cr) is larger than the capacitance on the stator 2 side (stator capacitance Cs), that is, Cr> Cs. By attaching the conductive sheet (conductive member) 6 described later to the permanent magnet motor 1 in this state, the capacitance of Cs can be easily increased and the capacitance of Cs can be brought closer to the capacitance of Cr. .. As a result, the shaft voltage | Vs-Vr | can be reduced to suppress the occurrence of electrolytic corrosion in the bearing.

A conductive sheet (conductive member) 6 is attached to the outer peripheral surface 14 (surface) of the motor outer shell 10 so as to cover at least a part of the conductive member 5. At least a part of the conductive sheet 6 faces the stator core 21 in the radial direction via the resin motor outer shell 10. In the present embodiment, the conductive sheet 6 is adhered to the motor outer shell 10 in a state of being in contact with the conductive member 5 (see FIGS. 5, 14 and the like).

As a result, the seat 6 and the stator core 21 function as a capacitor (capacitance), and the capacitance Cs on the stator 2 side can be increased. That is, when the conductive sheet 6 faces the stator core 21 of the conductor with the resin outer shell (motor outer shell) 10 of the insulator in between, charges are accumulated between the two conductors of the sheet 6 and the stator core 21. ..

When the conductive sheet 6 does not cover the conductive member 5 at all (when the conductive sheet 6 does not overlap with the conductive member 5 in the radial direction of the motor), the stator capacitance Cs depends on the presence or absence of the sheet 6. It is known that there is almost no change in. For example, when the conductive sheet 6 attached to the outer peripheral surface 14 of the motor outer shell 10 is arranged 1 cm away from the conductive member 5 in the circumferential direction of the motor, the stator capacitance Cs does not increase due to the sheet 6. It is presumed that this is because when the conductive sheet 6 does not cover the conductive member 5 at all, the conductive sheet 6 is in a state of being electrically floated, so that the conductive sheet 6 does not function as a capacitor. Will be done.

As will be described in detail later, the size of the stator capacitance Cs that increases when the conductive sheet 6 covers at least a part of the conductive member 5 is the size of the area of the region overlapping the stator core 21 of the sheet 6 in the radial direction. It is estimated that it is roughly proportional to the static electricity. Therefore, in the present embodiment, the seat 6 is arranged in the region where the stator core 21 is projected in the outer diameter direction on the surface of the motor outer shell 10 (see FIG. 7). As a result, the capacitance Cs on the stator 2 side can be appropriately adjusted so that the sheet 6 contributes to the increase in the stator capacitance Cs without waste.
In the present embodiment, the sheet 6 is formed so that the angle θ in the circumferential direction formed by the sheet 6 attached on the outer peripheral surface 14 of the motor outer shell 10 around the rotation axis C is, for example, about 30 °. (See Figures 5 and 7 etc.). This angle θ can be arbitrarily changed according to the desired capacitance Cs. For example, the seat 6 may extend over the entire circumference (so that θ = 360 °) in the circumferential direction of the motor outer shell 1. Similarly, the dimensions of the seat 6 in the rotation axis C direction can be arbitrarily changed.

As shown in FIG. 5, the sheet 6 has a rectangular shape and is arranged so that the long sides intersect the axis direction of the rotation axis C. In this embodiment, the long sides of the sheet 6 are arranged orthogonal to the axial direction of the rotation axis C. As a result, even when the motor 1 is small in the rotation axis C direction, the area of the conductive sheet 6 can be increased, and the capacitance Cs on the stator 2 side can be further increased. As a matter of course, the shape of the sheet 6 can be arbitrarily changed such as a rhombus, a circle, and a square.
In the present embodiment, although not shown, the conductive sheet 6 is formed by depositing a metal such as aluminum on the front surface of a thin plate (sheet) made of PET material and providing an adhesive surface on the back surface. In other words, the sheet 6 is formed by adhering a metal to a thin resin plate. By using a thin plate having an adhesive surface, the sheet 6 can be formed inexpensively and can be easily attached to the curved outer peripheral surface 14 of the motor outer shell 10 by adhesion. In this embodiment, the adhesive surface of the conductive sheet 6 is formed of a conductive adhesive. The adhesive surface of the conductive sheet 6 may be formed of an insulating material, and the conductive portion (metal or the like) of the sheet 6 and the stator core 21 are sandwiched between the insulating material (resin outer shell, adhesive surface). By being close to each other, it functions as a capacitor (capacitance).
Alternatively, as another embodiment, the sheet 6 may be formed of a sheet metal having a thickness of about 0.2 mm and may be fastened to the motor outer shell 10 with screws or the like.

Further, a rated name plate 7 may be attached to the outer peripheral surface 14 of the motor outer shell 10 separately from the seat 6 (see FIGS. 3, 5, and 7). The rating plate 7 is a name plate (label) on which values (rated values) such as specifications, performance, and usage limits under specified conditions are described for equipment, devices, parts, and the like.
The rated name plate 7 may be made of the same material as the sheet 6. As a result, the material used as the rated name plate 7 can be diverted to the sheet 6, or the material used as the sheet 6 can be diverted to the rated name plate 7, and the manufacturing cost can be reduced.

Further, in the present invention, the rated name plate 7 may be used as the sheet 6 as another embodiment in which the rated name plate 7 is formed of the same material as the sheet 6. That is, the rated name plate 7 made of a conductive material may be attached to the position of the sheet 6 in FIG. 7. As a result, since the rated name plate 7 functions as the seat 6 of the present invention, it is not necessary to separately prepare the seat 6, and the manufacturing cost of the permanent magnet motor 1 can be reduced.

FIG. 9 shows the output waveform of the shaft voltage in the motor (comparative example) in the state where the conductive sheet 6 is not attached, and FIG. 10 shows the conductive sheet 6 attached to the electric motor in the comparative example. It is an output waveform of the shaft voltage in the motor 1 of an Example. The sheet 6 is a rectangular thin plate having a width of 3.0 cm, a depth (height) of 2.0 cm, and a thickness of about 0.05 mm. In any case, the driving conditions of the motor were such that the applied voltage was DC380V and the rotation speed was 1,520 rotations / min.
Comparing these two figures, the maximum value of the shaft voltage on the + side is 2.34V and the maximum value on the-side is -1.68V in the comparative example (without sheet 6), whereas the maximum value on the-side is -1.68V, whereas the maximum value on the-side is -1.68V. Yes), the maximum value on the + side of the shaft voltage is 1.48V, and the maximum value on the-side is -0.77V. That is, it can be seen that by attaching the conductive sheet 6 to the motor 1, the maximum value of the shaft voltage can be reduced to about half as compared with the case where the conductive sheet 6 is not attached.

FIG. 11 is a graph showing the stator capacitance Cs with respect to the area change of the conductive sheet 6.
As shown in this figure, the stator capacitance Cs is linear with respect to changes in the area _ACS of the conductive sheet 6.

Specifically, the stator capacitance Cs is
[Equation 1]
Cs = C ₀ + kεA _CS / d
Can be expressed by the relational expression.
Here, C ₀ is the stator capacitance when there is no conductive sheet 6, k is a coefficient determined by the shape of the motor such as the bracket 41, and ε is the resin outer shell 10 existing between the sheet 6 and the stator core 21. The dielectric constant, _ACS is the area of the conductive sheet 6, and d is the distance between the opposing sheet 6 and the stator core 21 via the resin outer shell 10.
That is, the stator capacitance Cs can be easily adjusted by changing the area _ACS of the conductive sheet 6.

FIG. 12 is a perspective view showing a part of the electric motor 1 without the conductive sheet 6 according to the present invention. In FIG. 12, the resin outer shell 10 is transmitted and displayed.
As another embodiment of the present invention, in addition to the conductive sheet 6, the stator capacitance Cs may be further adjusted by changing the width W of the conductive member 5.
Table 1 and FIG. 13 show the stator capacitance Cs with respect to the change in the width W of the conductive member 5.

As shown in Table 1 and FIG. 13, it can be seen that when the width W of the conductive member 5 is increased by 1 mm from 5.0 mm to 10 mm, the stator capacitance Cs increases approximately linearly. That is, the stator capacitance Cs can also be increased (+4.75pF) by increasing the width W of the conductive member 5 (for example, changing from 5.0 mm to 10 mm).

FIG. 14 is a partial side perspective view showing the electric motor 1 provided with the conductive sheet 6 according to the present invention. That is, No. 1 in Table 1. The motor 1 of the embodiment has a conductive sheet 6 attached to the motor of 1 (comparative example).
Table 2 and FIG. 15 show the stator capacitance Cs with respect to the change in the area _ACS of the rectangular conductive sheet 6. The area _ACS of the seat 6 is H for the height of the seat 6 (the length of the seat 6 in the rotation axis C direction of the motor 1) and T for the width of the seat 6 (the length of the seat 6 in the circumferential direction of the motor 1). Then, it is obtained by A _CS = T × H (mm ² ). In this embodiment, the case where the area _ACS of the seat 6 is changed by changing the height H of the seat 6 is illustrated. In Table 2, instead of the width T (mm) which is the length dimension, the angle θ (°) formed by the sheet 6 attached on the outer peripheral surface 14 of the motor outer shell 10 around the rotation axis C (FIG. 7). , 14 is the angle formed by the two line segments connecting both ends of the sheet 6 in the circumferential direction and the rotation axis C) as a representative value. At this time, the width T (mm) is T = π × r × θ / 180, where π is the circumference ratio when the distance from the rotation axis C to the outer peripheral surface 14 of the motor outer shell 10 is the radius r (mm). Can be found at. In this embodiment, r = 46 (mm).

As shown in Table 2 and FIG. 15, No. 7-No. In 9, the width T of the conductive sheet 6 is constant (angle θ = 40 °), while the height H is changed stepwise, so that the stator capacitance accompanying the change in the area _ACS of the sheet 6 The change in capacitance Cs is measured. It can be seen that as the area _ACS of the conductive sheet 6 decreases, the stator capacitance Cs also gradually decreases.
Further, from Tables 1 and 2, No. 1 of the example provided with the conductive sheet 6 is provided. 7-No. In any case of No. 9, which is a comparative example not provided with the conductive sheet 6, No. It can be seen that the stator capacitance Cs is increased (+6.10 to + 10.46pF) more than 1.

That is, as shown in Tables 1 and 2 and FIG. 14, the motor 1 (No. 7 to No. 9 in Table 2) of the embodiment provided with the conductive sheet 6 includes the conductive sheet 6. The stator capacitance Cs can be made larger than that of the motor of the comparative example (No. 1 in Table 1). Further, it can be seen that the amount of increase in the stator capacitance Cs due to the provision of the conductive sheet 6 is substantially linear with the amount of increase in the area _ACS of the conductive sheet 6. Therefore, in the electric motor 1 of the embodiment, the stator capacitance Cs can be easily adjusted by changing the area _ACS of the conductive sheet 6.
In this embodiment, the area _ACS of the seat 6 is changed by changing the height H of the seat 6 (the length of the seat 6 in the rotation axis C direction of the motor 1), but the conductive seat. The area _ACS of the seat 6 may be changed by changing the width T (the length of the seat 6 in the circumferential direction of the motor 1) of 6.

As described above, in the present embodiment, a conductive sheet (conductive member) that covers at least a part of the conductive member is attached to the outer peripheral surface 14 (surface) of the outer peripheral surface of the motor. Therefore, when the conductive sheet and the stator core face each other via the resin outer shell, the conductive sheet functions as a capacitor and adjusts the capacitance (increases the capacitance Cs on the stator side). can. In particular, since the amount of increase in capacitance is proportional to the area of the conductive sheet, the capacitance on the stator side can be easily adjusted by changing the area of the conductive sheet.
As a result, the balance between the capacitance on the stator side and the capacitance on the rotor side can be easily adjusted, and the shaft voltage can be reduced to suppress the occurrence of electrolytic corrosion.

1 ... Motor 10 ... Motor outer shell (resin outer shell)
13 ... End face 105 ... Notch groove 2 ... Stator 21 ... Stator core 3 ... Rotor 32 ... Shaft 33 ... First bearing 34 ... Second bearing 41 ... Bracket 44 ... End face 5 ... Conductive member 6 ... Conductive sheet ( Conductive member)
7 ... Rated name plate C ... Rotating shaft

Claims

Rotor and
A shaft that is arranged along the axis of rotation of the rotor and to which the rotor is fixed,
The first bearing arranged on one end side of the shaft and
The second bearing arranged on the other end side of the shaft and
The stator core arranged on the outer peripheral side of the rotor and
The resin outer shell that covers the stator core and
An electric motor including a conduction member for electrically connecting the outer rings of each of the first bearing and the second bearing.
An electric motor to which a conductive member covering at least a part of the conductive member is attached to the surface of the resin outer shell.
The electric motor according to claim 1.
The conductive member is an electric motor in which at least a part of the conductive member faces the stator core in the radial direction via the resin outer shell.
The electric motor according to claim 1 or 2.
The conductive member is a motor that is in contact with the conductive member.
The electric motor according to any one of claims 1 to 3.
The conductive member is an electric motor formed by adhering metal to a thin resin plate.
The electric motor according to any one of claims 1 to 4.
The conductive member is an electric motor having an adhesive surface.
The motor according to any one of claims 1 to 5.
The conductive member is an electric motor arranged in a region where the stator core is projected in the outer diameter direction on the surface of the resin outer shell.
The electric motor according to any one of claims 1 to 6.
The conductive member is a rectangular electric motor, and the long sides of the conductive member are arranged so as to intersect in the axial direction of the rotation axis.
The motor according to any one of claims 1 to 7.
A rated name plate is attached to the surface of the resin outer shell.
The rated name plate is an electric motor made of the same material as the conductive member.